[46P.07] Deposition Surface Properties and the Spectra of Deposited Ices

The spectra of adsorbed species, especially thin films, are
known to show effects related to the nature of the
deposition surface. Subtle effects, such as shifts in line
positions, are common, and must be recognized to ensure
proper spectral assignments of the deposited material. We
have also observed more dramatic effects, including low
temperature crystallization (LTC), which appears to be
surface-dependent as well. Here, the ice film forms in the
crystalline phase at deposition temperatures well below the
amorphous-to-crystalline transition point. Since astronomers
often use the phase of the deposited ice to give important
clues about the thermal- and radiation-history of the
object, a better understanding of the effect of the surface
on the spectrum of the deposited ice is required. To that
end, we have measured a number of surface properties
(surface area, pore volumes, and pore size distributions)
for a variety of amorphous silicate interstellar grain
analogs, and have studied the IR spectra of methanol (and
other ices) deposited on these materials. Thermally induced
modifications to some of these surfaces have also been
examined. Results and correlations among the data will be
presented.